Analysis on the Corrosion Rust of Carbon Steel Exposed to Salt Lake Area for 25 Months

The rust layers formed on upward and downward surfaces of carbon steel exposed to salt lake atmosphere for 25 months were investigated by scanning electron microscopy (SEM), electron probe micro analyzer (EPMA), X-ray diffraction (XRD), infrared transmission spectroscopy (IRS), and electrochemical techniques. The depths of rust layers on upward and downward surfaces were similar to each other. The corrosion products on the two surfaces were mainly composed of beta-FeOOH, Fe-8(O,OH)(16)Cl-13, and a little gamma-FeOOH. delta-FeOOH and Fe3O4 were only detected in outer part of the rust layers. The results of electrochemical analysis showed that the rust layer suppressed the corrosion of steel substrate and the corrosion resistance of rust layers increased with time.